Methods of producing printing plates or the like



Patented Dec. 8, 1931 UNITED STATES PATENT orrlcs AXEL WILLIAM NORDLANDER, or scrocxnonm, swnnnn, assrenon 17o ammomen'r narrnosnarr, or STOCKHOLM, swnnnn, a COMPANY or swnmnw METHODS OEPRODUCING PRINTING PLATES OR THE LIKE No Drawing. Application filed March 7, 1 928, Seria1 No. 259,920, and in Sweden March 18, 1927. Y

The present invention relates to a method of producing printing plates or the like which light of printing plates from supported or non-supported layers or films containing one or several silver salts. The invention is characterized principally by the fact that. the layer or film prior to exposure is treated with one or several hardening agents such as alum, formaline, chrome alum and so forth. The hardened layer' is then treated with a solution of one or several light-sensitive chromium salts, exposed to the action of light and subjected to an after-treatment with acid or acids, when the layer, for instance by being moistened and treated with a fat dye or ink, may immediately be used either for direct printing or for transfer of the image, for in stance upon zinc and subsequent treatment in known manner.

This method of producing printing plates or the like, which will be'more fully described in the following specification, offers considerable advantages in many respects over the methods heretofore used in the art.

Theplates produced according to the invention, it being understood that the word plate is used in the following to denote the supported as well as the non-supported layer or film, are characterized by greater lightsensitivity as compared with the plates or the like used in other similar processes, and consequently a considerably shorter time of exposure may be used. The reproduction on the plate of the image to be printed may be effected in known manner by direct printing from a negative in'so m'e cases a pos1tive,- or by direct exposure as in a camera, but such reproduction may also, as distinct from the' methods heretofore in use in the art of reproduction, be efiected without difficulty while the image is simultaneously being enlarged, for instance'by projection, which is of great such projection could not be practically carried outwith any reasonable degree ofenlargement, owing to A the very long time of exposure required there- .for. -Thus, ifan enlargement was to be produced according to any of-the known methods, it was necessary first of all to produce a negative of the same or about the same size as the desired printing plate, which represented a good deal of expense and loss of time. According to' the present invention, however, an enlargement may be made direct by projection and in a comparatively short period of time.

Another advantage which is characteristic of the method according to the present invention, is'that the exposed and after-treated plate may be used immediately for direct printing, and that a very great number of prints may be taken from the same plate without perce tible falling ofi' of the quality of the printed image. Theimage may also be transferredupon zinc in the usual way, for example for etching.

By a special procedure, which also forms an object of the invention, the sensitive layer may be mounted on the support, when such a support is being used, by means of an intermediate layer, which considerably increases the cohesion between the sensitive layer and the support. As a result of this powerful cohesion such .a material as for example a zinc-plate may be used as the support and the finished printin plate may be bent to be used for example for ofi-set printing without the layer, working loose from the support. 1

The method is suitable not only for the production of printing plates capable of reproducing the lightsand shadows of the original, but is also, by certain modifications, suited for production of so-called high and deep print stereotypes and screens.

The prints are distinguished by the exceedingly accurate reproduction of the de tails of the original as well as of the lights sensitive layer, in the following manner. The support is carefully cleaned, for instance with hot water, and is then coated with a solution of gelatine containing large quantities of water-glass, for instance one part of waterglass and five partsof saturated gelatine. The mixture is preferably prepared at a tem-. perature of 5060 degrees centigrade and must, when applied to the support, be kept warm as well as the latter. After cooling the support is ready to receive the sensitive layer.

This sensitive layer, which preferably consists of a silver salt-gelatine emulsion, may be prepared in the following manner. 100 grams of gelatine are placed in cold water for one hour, the excess of water is drained off and the saturated gelatine heated. When melted 10' grams of silver nitrate are added together with an equivalent quantity of sodium chloride and the mixture is boiled for 5' to 10 minutes, while being stirred, in nonactinic light, whereupon it is permitted to cool, when it will solidify. For washing out any excess of salts, the solidified mass is finely divided and washed in running water for about 12 hours. This stock mixture will kee .in a dark room.

hen used, one part of the stock mixture is boiled with two parts of gelatine saturated with water in non-actinic'light during a period of about 5 minutes. The mixture .is permitted to cool to about 40 degrees centigrade, when it is poured out on the prepared supports, which are then allowed to dry. By

dilution or concentration of the silver saltgelatine mixture and by controlling the temperature at which the coating of the supports takes place, the thickness of the layer and thus, to a certain extent, the printing effect thereof, may be varied at will.

When dry, the layer is hardened in a solution of alum, formaline, chrome alum or the like. A suitable bath for this purpose consists of a saturated solution of alum in water. In this bath the silver salt-gelatine layer is hardened for about 5 minutes, whereupon the plates are washed and dried. Plates produced in this manner will keep in a dark room.

The hardening mayalso be carried out b first subjecting the layer to a pre-hardening with alum and then to an after-hardening with formaline, for instance one part of formaline to 2540 parts of water. In this way a harder layer is obtained.

To prevent the gelatine layer from working loose from the support during the aftertreatment, the edges of the layer are preferably coated with a solution of shellac.

If a printing plate is to be produced from these stock plates, the gelatine .layer is bathed in an 8% solution of ammonium bichromate admixed with ammonia until the solution has assumed a light yellow colour one part of ammonia to ten parts of bichromate solution. The plate is dried at a tem perature of 40-45 degrees centrigrade, which requires a time of about two hours, more or less, depending on the thickness of the gelatine layer, and is then ready to take up the desired image by exposure, which may take place in different ways as stated hereinbefore, inter alia also by projection under simultaneous enlargement of the image. The importance of this has already been pointed out, and as an example of the short periods of exposure which can be employed, it may be mentioned that the time of exposure for making a stereotype of the dimensions 20-26 centimeters from a negative 9-12 centimeters, usinga 30 ampere arc lamp, is about 5 minutes only. With regard to the source of light, it should "of course be observed, that in order to obtain as short an exposure as possible, the source of light should give off a suflicient quantity of actinic or short-wave light.

In certain cases it may be preferable to undertake a hardening also after the exposure.

The exposed plate is then subjected to an after-treatment with acids. A suitable solu- 'tion for this purpose may consist of 1 part of sulphuric acid and 15 parts of water; the ,time of treatment is generally 1-2 minutes depending on the time of exposure and other circumstances.

It is of importance that the edges of the gelatine layer are coated with shellac prior to the after-treatment in order to prevent liqaid from entering the space between the layer and the support and thus separating them. The printing plate may be used immediately for printing in a press, for instance by being moistened and treated with fat dye or colouring matter, or the image may be transferred in known manner for instance upon zinc for etching.

For the production of screens the sensitive layer is exposed directly in evenly distributed or diffused light, a stipple or grain structure being then obtained after the acid treatment, said structure having requisite screening effect. Itis also possible, however, to expose through one of the screens used in the art of reproduction, the procedure otherwise being the same as described.

v Deep-print stereotypes may be produced by exposing through a negative and treating the surface, subsequent to after-treatment and moistening, with fat colouring matter, whereupon the plate is dried.

High-print stereotypes may be produced in a similar manner, with the difference only that the plate is exposed to the action of light through a positive.

The whole process as hereinbefore described represents a great saving of time, inasmuch as finished stereotypes having the same size as the original picture or layer or smaller may be produced in a few hours or even in a shorter time from the stock plates.

What I claim is 1. The process of making a printing plate which can be used for direct printing, comprising incorporating in a colloid film a silver halid, hardening the film, treating the hardened film with an alkali bichromate, exposing the film to the action of light and selectively'modifyin the hardening with an agent of suitable p ll-concentration.

2. A process as defined in claim 1 in which the silver halid is silver chloride.

3. A process asdefined in claim 1 in which the hardening agent is alum.

4. A process as defined in claim 1 in which the silver halid is silver chloride and the hardening agent is alum.

5. A process as defined in claim 1 in which the alkali bic'hromate is used in the form of a solution of ammonium-bichromate admixed with ammonia. I

6. The process of making-a printing plate which can be used for direct printing, comprising incorporating in a colloid film silver chloride, hardening the film with alum, treating the hardened film with a solution of ammonium bichromate admixed with ammonia, exposing to the action of light and selectively modifyin the hardening with an agent of suitable p -concentration.

7. A process as defined in claim 1 in which the agent employed for modifying the hardening is an acid.

8. A process as defined in claim 6 in which the agent employed for modifying the hardening is an acid.

9. A process as defined ,in claim 6' in which the agent employed for modifying the hardening is diluted sulfuric acid.

10. The process of making a printing plate which can be used for direct printinggcomprising incorporating silver chloride in gelatine, hardening the gelatine with alum, treating the hardened gelatine with a solution of ammonium bichromateadmixed with ammonia, exposing to the action of light and selectively modifying the hardening with diluted sulfuric acid.

11. The process of making a printing plate which can .be used for direct printing, comprising incorporating a silver halid in gelatine, hardening the gelatine with a hardening agent, treatingthe harder ed gelatine with a solution of an alkali bichromate, exposing to the action of light while enlarging and modifying the hardening with an acid.

12. The process of making a printing plate which can be used for direct printing comprising incorporating a silver halid in gelatine, hardening the gelatine with a hardening agent, treating the hardened gelatine with a'solution of an alkali bichromate, exposing to the action of light, hardening again and selectively modifying the hardening with an acid. 13. The process of making a stereotype which can be used for direct printing, comprising incorporating a silver halid and an alkali bichfomate in a colloid film, exposing to the action of light,-selectively modifying the hardening with an agent of suitable pH- concentration, moistening and rolling over the treated surface with dye and drying.

14. A process of making a stereotype ing a printing plate comprising a hardened gelatine film in which is incorporated silver chloride and ammonium bichromate.

' In testimony whereof I, aflix my signature. AXEL WILLIAM NORDLANDER. 

